What is the recommended insulin dosage, frequency, and duration for diabetes management?

Insulin Dosing, Frequency, and Duration for Diabetes Management

Initial Dosing Strategy

For Type 2 diabetes, start basal insulin at 10 units once daily or 0.1-0.2 units/kg/day, administered at the same time each day, and titrate by 2-4 units every 3 days until fasting glucose reaches 80-130 mg/dL. 1, 2, 3

Type 1 Diabetes Dosing

• Total daily insulin requirement: 0.5 units/kg/day for metabolically stable patients (acceptable range 0.4-1.0 units/kg/day), with approximately 50% as basal insulin and 50% as prandial insulin divided among meals 1, 4
• For patients presenting with diabetic ketoacidosis, higher weight-based dosing than 0.5 units/kg/day is required 4
• Young children and those in the "honeymoon period" with residual insulin production require lower doses of 0.2-0.6 units/kg/day 4
• Rapid-acting insulin analogue should be given 0-15 minutes before meals 5

Type 2 Diabetes Dosing

• Insulin-naive patients: Start with 10 units once daily or 0.1-0.2 units/kg/day of basal insulin 1, 2, 3, 6
• For severe hyperglycemia (blood glucose ≥300-350 mg/dL and/or A1C ≥10-12% with symptomatic features), start basal-bolus insulin immediately at 0.3-0.5 units/kg/day total daily dose 2, 3
• Continue metformin unless contraindicated when initiating insulin therapy 1, 3, 5

Titration Protocol

Basal Insulin Adjustment Algorithm

• Increase by 2 units every 3 days if fasting glucose is 140-179 mg/dL 2, 3
• Increase by 4 units every 3 days if fasting glucose is ≥180 mg/dL 2, 3
• Target fasting plasma glucose: 80-130 mg/dL 1, 2, 3
• If hypoglycemia occurs without clear cause, reduce dose by 10-20% immediately 2, 3

Critical Threshold: When to Stop Escalating Basal Insulin

When basal insulin exceeds 0.5 units/kg/day and approaches 1.0 units/kg/day, add prandial insulin rather than continuing to escalate basal insulin alone. 1, 2, 3

Clinical signals of "overbasalization" include:

• Basal insulin dose >0.5 units/kg/day 2, 3
• Bedtime-to-morning glucose differential ≥50 mg/dL 2, 3
• Hypoglycemia episodes 2, 3
• High glucose variability 2, 3

Adding Prandial Insulin

Indications for Prandial Insulin

• After 3-6 months of basal insulin optimization, if fasting glucose reaches target but HbA1c remains above goal 2, 3
• When basal insulin approaches 0.5-1.0 units/kg/day without achieving A1C goal 2, 3
• Significant postprandial glucose excursions persist 2, 3

Prandial Insulin Initiation

• Start with 4 units of rapid-acting insulin before the largest meal or 10% of current basal dose 2, 3
• Add prandial insulin before the meal causing the greatest glucose excursion 2, 3
• Titrate by 1-2 units or 10-15% every 3 days based on postprandial glucose readings 2, 3

Frequency and Timing

Basal Insulin Administration

• Once daily administration at the same time each day (can be given at breakfast, dinner, or bedtime) 3, 7, 8
• For insulin detemir, if once-daily dosing is insufficient, administer twice daily with evening dose either at dinner, bedtime, or 12 hours after morning dose 8
• For insulin glargine administered twice daily, divide total daily dose equally between morning and evening 2

Timing Considerations

• Blood glucose levels rise around the time of insulin glargine injection regardless of whether given at lunch, dinner, or bedtime 9
• Bedtime injection leads to hyperglycemia in the early part of the night, which is improved by giving insulin glargine at lunch or dinner 9
• For patients on glucocorticoids, consider administering NPH insulin in the morning to counteract steroid-induced daytime hyperglycemia 2

Duration of Therapy

Insulin therapy is lifelong for Type 1 diabetes and typically long-term for Type 2 diabetes once initiated, with ongoing dose adjustments based on glycemic control. 5, 10

• Assess adequacy of insulin dose at every clinical visit 2, 3
• Daily self-monitoring of fasting blood glucose is essential during titration 2, 3
• Reassess every 3 days during active titration and every 3-6 months once stable 2

Special Populations Requiring Dose Adjustments

Higher Insulin Requirements

• Puberty: Doses approaching 1.0 units/kg/day or more 1, 4
• Pregnancy requires higher doses 1, 4
• Medical illness (infections, inflammation) increases requirements 1, 4
• Menses may increase insulin needs 1, 4

Lower Insulin Requirements

• Elderly patients (>65 years): Start with 0.1 units/kg/day 2, 3
• Renal impairment requires lower starting doses 2, 3
• Poor oral intake necessitates dose reduction to 0.1-0.25 units/kg/day 2, 3

Hospitalized Patients

• For insulin-naive or low-dose insulin patients: 0.3-0.5 units/kg/day total daily dose, with half as basal insulin 3
• For patients on high-dose home insulin (≥0.6 units/kg/day): Reduce total daily dose by 20% to prevent hypoglycemia 2, 3

Common Pitfalls to Avoid

• Never delay insulin initiation in Type 2 diabetes patients not achieving glycemic goals with oral medications 3
• Do not continue escalating basal insulin beyond 0.5-1.0 units/kg/day without addressing postprandial hyperglycemia 2, 3
• Avoid using sliding scale insulin alone, especially in Type 1 diabetes 2
• Do not use premixed insulin in hospital settings due to high hypoglycemia risk 2, 3
• Never abruptly discontinue oral medications when starting insulin due to rebound hyperglycemia risk 5
• Do not dilute or mix insulin glargine with other insulins due to its low pH 3
• Avoid injections into lipohypertrophic areas as this distorts insulin absorption 5
• When transitioning from IV to subcutaneous insulin, ensure overlap to prevent rebound hyperglycemia 2

Injection Technique

• Use the shortest needles (4-mm pen and 6-mm syringe needles) as first-line choice in all patients 5
• Rotate injection sites within the same region (thigh, abdominal wall, or upper arm) 7, 8
• Avoid intramuscular injections, especially with long-acting insulins, as severe hypoglycemia may result 5